CNC Router V1.0 (For Cutting Multiple Materials)

**JAZZCNC** · 20-11-2015

Originally Posted by biketrialsdave

OK, I'll get onto that tomorrow! I assume 2 linear rails with the ballscrew in-between them sitting in a slot to reduce the overall depth? I'm using THK HSR15 carriages for the other axis, I assume these will be OK for the Z too?

Yes more than enough regards forces etc but has pointed out by neale 20mm can work better regards spacing etc. Personally I use 20mm on all axis for simplicity and hardly any difference in price.

Originally Posted by biketrialsdave

The drop brackets on the rear are 5mm steel at the moment. I can increase this and also add some kind of right angle bracket perhaps.

Yes you need more bracing to stop deflection. 5mm steel isn't really upto to it without being braced.

**routercnc** · 20-11-2015

I have 15mm rails on Z and they work ok but they use M3 bolts on the rail and carriages which look very small compared to M5 on the 20mm rails on my Y axis. When cutting I can feel vibration across them especially the top ones and for this type of machine I would go with 20mm on Z.

**biketrialsdave** · 30-12-2015

Hmm maybe I will stick with one motor and use a single large belt. I don't think it will require much modification (whilst still having the potential to run 2 motors in the future). Just need to make sure I can tension the belt well. I'm thinking of a simple idler pulley which I can slide in a slot.

**Clive S** · 30-12-2015

Originally Posted by biketrialsdave

Hmm maybe I will stick with one motor and use a single large belt. I don't think it will require much modification (whilst still having the potential to run 2 motors in the future). Just need to make sure I can tension the belt well. I'm thinking of a simple idler pulley which I can slide in a slot.

You will need to make sure there are enough teeth engaged on the pulley with the belt. Also if you want to put material through the back of the machine the belt would have to be routed accordingly.

**biketrialsdave** · 30-12-2015

Something like below? The bottom idler pulleys on both sides sit in slots for adjusting tension.

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**cropwell** · 30-12-2015

You don't need to spend money on pulleys just to use them as tensioners.

**JoeHarris** · 30-12-2015

What ability have you got for machining the aluminium? If only basic tools like me then you could probably lose some of the pockets. Would help with adjustment later too ?

**JAZZCNC** · 30-12-2015

Too many idlers drop try to keep to a minimum you'll get away with just one. Belt will be above the profile but doesn't matter because you'll want to cover it up anyway.

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**JoeHarris** · 01-01-2016

Originally Posted by JAZZCNC

Too many idlers drop try to keep to a minimum you'll get away with just one. Belt will be above the profile but doesn't matter because you'll want to cover it up anyway.

Jazz, is there enough engagement on the top right pulley? What's the minimum? you could add one more like this?? I

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**Jonathan** · 01-01-2016

Originally Posted by JoeHarris

Jazz, is there enough engagement on the top right pulley? What's the minimum? you could add one more like this?? I

The spec. for HTD belts say make sure to have 5 teeth engaged. This is based on ensuring that with a sufficiently high load, the belt will snap instead of the teeth ripping off. This hardly matters to us, as we're not using the belts at close to their load ratings, however we do want to get good stiffness from the belts (especially with such a long best) so it seems a reasonable baseline to design for at least 5 teeth engaged.